Delivery systems have been known for many years, for use with the Seldinger technique and related percutaneous entry techniques for vascular delivery of implants into the vasculature of human or veterinary patients. Such systems typically utilize a wire guide inserted into the vasculature to extend to the site of implantation of a medical device such as a stent, stent graft, filter, occluder, valve or the like. An introducer sheath is placed over a portion of the guide wire, and a catheter inserted over the guide wire within the introducer sheath and beyond its distal tip, with the implant contained within a distal portion of the catheter until the implant is delivered to the site of implantation. The implant is then released from the catheter distal tip and deployed. The insertion and progress of the procedure are monitored closely through fluoroscopy, angiograms or CT scanning or the like, in which radiopaque markers are commonly used as landmarks on the wire guide, catheter and implantable device to assure eventual accurate positioning of the device at the site of implantation and its full deployment.
One delivery system is known from U.S. Pat. No. 4,494,531 for delivery of a vena cava filter into the vena cava of the vasculature. The system includes a wire guide with a handle, and a cartridge catheter contains the filter at its distal end in a reduced diameter confinement and having a rear assembly. Once access is gained to the vasculature by an introducer sheath and a dilator, and the dilator is removed from the sheath, the cartridge catheter is inserted through the sheath until its distal end reaches the deployment site, whereafter the collapsed filter is deployed by gradually retracting the catheters distal end, while the filter is held axially fixed by a positioning wire guide extending to the proximal end of the filter, to initially expose the distal end of the filter having outwardly curving struts with barbs. The exposed filter then expands so that its distal barbs engage and seat in the vessel wall in cooperation with sharp, forward jabs or manipulation of the catheter, and then the remainder of the filter forms a “bird's nest” and its proximal barbs engage and seat in the vessel wall to anchor the filter in position as the catheter continues to be retracted. The particular filter disclosed in the patent is sold by Cook Incorporated, Bloomington, Ind. as the Gianturco-Roehm BIRD'S NEST Vena Cava Filter.
Delivery systems for filters are also disclosed in U.S. Pat. Nos. 5,329,942 and 5,324,304, wherein the filter is released at the deployment site by retraction of the catheter distal end from therearound as the proximal filter end is held in place axially.
It is desired to provide a delivery system for medical devices such as vascular valves that provides for assuredly centering the distal ends of valves during deployment from the delivery catheter.
It is also desired to provide such a medical device delivery system that does not interfere with precise visualization of radiopaque markers on the medical device such as a vascular valve being implanted.
It is further desired to provide such a delivery system to have a minimized diameter for use with medical devices such as vascular valves containing lyophilized tissue that enables hydration of the lyophilized tissue at the time of delivery into the patient.